1,25(OH)2D3 is an antiproliferative agent that may inhibit proliferation of
breast cancer (BC) cells in vitro and BC development in animals. Epidemiological studies have shown a high incidence of BC in people less exposed to solar rays. To unravel the role of
Vitamin D3 in BC patients, we have investigated serum levels of 25(
OH)D3 and its active form
1,25(OH)2D3 as well as tissue expression of 1alpha-hydroxylase, 24-hydroxylase, and
Vitamin D-receptor (VDR), determined by semiquantitative RT-PCR, in 88 Brazilian BC patients and 35 women without
cancer (submitted to
mammoplasties or resection of benign lesions). Median age of women with and without
cancer was 51 and 46 years, respectively, and the majority of BC patients were classified as clinical stage II (67%). Although no differences in 25(
OH)D3 serum concentration were found,
1,25(OH)2D3 (40+/-21 pg/ml) levels in BC patients were lower than in women without
cancer (53+/-23). Our results indicate that 24-hydroxylase, VDR and 1alpha-hydroxylase
mRNA tissue expression is similar in both groups and no correlation between 24-hydroxylase, 1alpha-hydroxylase, and VDR expression in
breast tumors was found. A low
1,25(OH)2D3 serum concentration seems to be associated to
breast cancer, however, the mechanism involved in this regulation is still unclear.